Study of liquid-liquid two-phase flow in hydrophilic nanochannels by molecular simulations and theoretical modeling

Multiphase flow in nanoporous media is ubiquitous in geophysics, physical chemistry, and bioengineering. The underlying mechanisms of two-phase flow are of great importance in the prediction of water and oil flow in shale nanoporous media. In this work, we use molecular dynamic simulations to investigate a laminar type oil–water two-phase flow (OW2PF) in quartz nanopores. We find that in nanochannels, due to liquid–liquid slip, the enhancement in oil phase flow may not be neglected. As water film thickness and pore size increase, such enhancement decreases gradually. According to MD results, a new hydrodynamic flow model considering fluid distributions, heterogeneous fluid properties, liquid-wall interaction, and liquid–liquid slip is proposed and compared to MD results and other hydrodynamic flow models. While previous hydrodynamic flow models generally underestimate oil phase flow in a laminar type OW2PF in quartz nanopores, our model shows an excellent agreement with MD simulations for a wide range of pore sizes. Our work could shed some lights into flow mechanism of a laminar type OW2PF in nanoporous media and provide insights into flow modeling development in shale oil exploitation.